Toner, toner cartridge, and image forming apparatus

ABSTRACT

According to one embodiment, a toner contains a toner mother particle and an external additive. The toner mother particle contains a crystalline polyester resin and a specific ester wax. The external additive contains silica A having a D50 of 10 nm to 14 nm and monodispersed silica B having a D50 of 90 nm to 150 nm. The following conditions are satisfied. Content of silica A: 0.1 parts by mass to 0.8 parts by mass with respect to 100 parts by mass of the toner mother particle. Content of silica B: 0.3 parts by mass to 1.2 parts by mass with respect to 100 parts by mass of the toner mother particle. Ratio (content of silica B/content of silica A): 1.0 to 5.0. Residual ratio X of silica A: 70% or more. Residual ratio Y of silica B: 30% or more. Ratio (residual ratio X/residual ratio Y): 1.0 to 3.0.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2021-156537, filed on Sep. 27, 2021, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate to a toner, a toner cartridge, andan image forming apparatus, and method of making the toner.

BACKGROUND

A toner containing a crystalline polyester resin is known. Alow-temperature fixing toner containing a crystalline polyester resin isexcellent in low-temperature fixability.

However, when an image forming apparatus in which the low-temperaturefixing toner is adopted is operated in a high-temperature environment,the following problems occur.

-   -   As a temperature in a machine body of the image forming        apparatus increases, a developer containing the low-temperature        fixing toner becomes a cake. As a result, the caked developer is        clogged in a conveyance unit in a developing device, thereby        causing an image defect.    -   Since hygroscopicity of the crystalline polyester resin is high,        a charge amount of the toner decreases, and toner scattering        deteriorates. As a result, toner contamination occurs in the        machine body.

Therefore, it is very difficult to maintain storage stability and thecharge amount in a high-temperature environment while maintaining thelow-temperature fixability in the low-temperature fixing toner. Inparticular, in an image forming apparatus provided with a recyclingsystem, a toner from which an external additive is detached from asurface may return to the developing device to be recycled. Therefore,caking and a decrease in charge amount are more likely to occur.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a schematic structure ofan image forming apparatus according to an embodiment;

FIG. 2 is a perspective view of a developing device;

FIG. 3 is a side view of the developing device;

FIG. 4 is a diagram illustrating an example of a schematic structure ofan image forming apparatus according to another embodiment; and

FIG. 5 is a perspective view of a modification of a developing device ofFIG. 4 .

DETAILED DESCRIPTION

In general, according to one embodiment, a toner that is excellent inlow-temperature fixability, excellent in storage stability in ahigh-temperature environment even when recycled, and is capable ofsufficiently maintaining a charge amount, and a toner cartridge and animage forming apparatus in which the toner is accommodated are provided.

According to an embodiment, a toner contains: a toner mother particle;and an external additive adhered to a surface of the toner motherparticle.

The toner mother particle contains a crystalline polyester resin, anester wax, and a colorant.

The external additive contains silica A and monodispersed silica B. Thesilica A has an average primary particle diameter D₅₀ of 10 nm to 14 nm.The monodispersed silica B has an average primary particle diameter D₅₀of 90 nm to 150 nm.

The ester wax is a condensation polymer of a first monomer group and asecond monomer group. The first monomer group includes at least threetypes of carboxylic acids. The second monomer group includes at leastthree types of alcohols.

A ratio of a carboxylic acid having 18 or less carbon atoms in the firstmonomer group is 5% by mass or less with respect to 100% by mass of thefirst monomer group. A ratio of an alcohol having 18 or less carbonatoms in the second monomer group is 20% by mass or less with respect to100% by mass of the second monomer group.

A ratio of a carboxylic acid having C_(n) carbon atoms, which is amaximum content in the first monomer group, is 70% by mass to 95% bymass with respect to 100% by mass of the first monomer group. A ratio ofan alcohol having C_(m) carbon atoms, which is a maximum content in thesecond monomer group, is 70% by mass to 90% by mass with respect to 100%by mass of the second monomer group.

A content of the silica A is 0.1 parts by mass to 0.8 parts by mass withrespect to 100 parts by mass of the toner mother particle.

A content of the silica B is 0.3 parts by mass to 1.2 parts by mass withrespect to 100 parts by mass of the toner mother particle.

A ratio of the content of the silica B to the content of the silica A is1.0 to 5.0.

A residual ratio X of the silica A calculated according to the followingequation (1) is 70% or more.

A residual ratio Y of the silica B calculated according to the followingequation (2) is 30% or more.

A ratio of the residual ratio X to the residual ratio Y is 1.0 to 3.0.

Residual Ratio X=(N _(a2) /N _(a1))×100 Equation (1)

Residual Ratio Y=(N _(b2) /N _(b1))×100 Equation (2)

In the equation (1), N_(a1) is the number of adhered silica A measuredfor a toner according to an embodiment, and N_(a2) is the number ofadhered silica A measured for a particle z obtained by the followingmethod Z.

In the equation (2), N_(b1) is the number of adhered silica B measuredfor the toner according to the embodiment, and N_(b2) is the number ofadhered silica B measured for the particle z obtained by the followingmethod Z.

Method Z: executing an ultrasonic treatment on an aqueous liquidcontaining the toner according to the embodiment, water, and asurfactant at 20° C. and 1000 Hz for 10 minutes, then centrifuging theobtained aqueous liquid at 20° C. and 1000 rpm for 15 minutes, removingthe separated external additive, and then executing drying to obtain theparticle z.

Hereinafter, a toner according to an embodiment will be described.

The toner according to the embodiment contains a toner mother particleand an external additive.

The toner mother particle contains a crystalline polyester resin, anester wax, and a colorant.

The external additive contains silica A and monodispersed silica B. Thesilica A has an average primary particle diameter D₅₀ of 10 nm to 14 nm.The monodispersed silica B has an average primary particle diameter D₅₀of 90 nm to 150 nm.

The crystalline polyester resin will be described.

The crystalline polyester resin functions as a binder resin. In theembodiment, a polyester resin, in which a ratio of a softeningtemperature to a melting temperature (softening temperature/meltingtemperature) is 0.8 to 1.2, is referred to as a “crystalline polyesterresin”.

A polyester resin, in which the ratio of the softening temperature tothe melting temperature (softening temperature/melting temperature) isless than 0.8 or more than 1.2, is referred to as an “amorphouspolyester resin”.

Examples of the crystalline polyester resin include a condensationpolymer of a dihydric or polyhydric alcohol and a dihydric orpolycarboxylic acid.

Examples of the dihydric or polyhydric alcohol include ethylene glycol,1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-butenediol,polyoxypropylene, polyoxyethylene, glycerin, pentaerythritol, andtrimethylolpropane. As the dihydric or polyhydric alcohol,1,4-butanediol and 1,6-hexanediol are preferable.

Examples of the dihydric or polycarboxylic acid include: adipic acid,oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid,itaconic acid, glutaconic acid, succinic acid, phthalic acid,isophthalic acid, terephthalic acid, sebacic acid, azelaic acid,succinic acid substituted with an alkyl group or an alkenyl group,cyclohexanedicarboxylic acid, trimellitic acid, and pyromellitic acid;acid anhydrides thereof; and esters thereof.

Examples of the succinic acid substituted with an alkyl group or analkenyl group include succinic acid substituted with an alkyl group oran alkenyl group having 2 to 20 carbon atoms. Examples thereof includen-dodecenyl succinic acid and n-dodecyl succinic acid. As the dihydricor polycarboxylic acid, fumaric acid is preferable.

However, the crystalline polyester resin is not limited to thecondensation polymer of the dihydric or polyhydric alcohol and thedihydric or polycarboxylic acid exemplified here. Any of the abovecrystalline polyester resins may be used alone, or two or more thereofmay be used in combination.

A mass average molecular weight of the crystalline polyester resin ispreferably 6×10³ to 18×10³, and more preferably 8×10³ to 14×10³. Whenthe mass average molecular weight of the crystalline polyester resin isequal to or greater than the above-mentioned lower limit, the toner isfurther excellent in low-temperature fixability. When the mass averagemolecular weight of the crystalline polyester resin is equal to or lessthan the above-mentioned upper limit, the toner is also excellent inoffset resistance.

In the present specification, the mass average molecular weight is avalue obtained by gel permeation chromatography in terms of polystyrene.

The melting point of the crystalline polyester resin is preferably 60°C. to 120° C., more preferably 70° C. to 115° C., and still morepreferably 80° C. to 110° C. When the melting point of the crystallinepolyester resin is equal to or higher than the above-mentioned lowerlimit, the toner is further excellent in heat resistance. When themelting point of the crystalline polyester resin is equal to or lowerthan the above-mentioned upper limit, the toner is further excellent inlow-temperature fixability.

The melting point of the crystalline polyester resin can be measured by,for example, a differential scanning calorimeter (DSC).

The toner mother particle may further contain a binder resin other thanthe crystalline polyester resin as long as an effect disclosed in theembodiment can be obtained.

Examples of other binder resins include an amorphous polyester resin, astyrene resin, an ethylene resin, an acrylic resin, a phenolic resin, anepoxy resin, an allyl phthalate resin, a polyamide resin, and a maleicacid resin. Among these, the amorphous polyester resin is preferable.

However, other binder resins are not limited to these exemplifiedresins. Any of the above other binder resins may be used alone, or twoor more thereof may be used in combination.

Examples of the amorphous polyester resin include a condensation polymerof a dihydric or polycarboxylic acid and a dihydric alcohol.

Examples of the dihydric or polycarboxylic acid include a dihydric orpolycarboxylic acid, an acid anhydride of a dihydric or polycarboxylicacid, and an ester of a dihydric or polycarboxylic acid. Examples of theester of a dihydric or polycarboxylic acid include a lower alkyl (having1 to 12 carbon atoms) ester of a dihydric or polycarboxylic acid.

Examples of the dihydric alcohol include ethylene glycol, diethyleneglycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol,1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol,1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol,polyethylene glycol, polypropylene glycol, polytetramethylene glycol,bisphenol A, hydrogenated bisphenol A, and an alkylene oxide adduct ofbisphenol A. However, the dihydric alcohol is not limited to theseexemplified alcohols.

Examples of the alkylene oxide adduct of bisphenol A include a compoundobtained by adding an average of 1 to 10 moles of an alkylene oxidehaving 2 to 3 carbon atoms to bisphenol A. Examples of the alkyleneoxide adduct of bisphenol A includepolyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene(3.3)-2,2-bis(4-hydroxyphenyl)propane,polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene(2.0)-polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane,and polyoxypropylene(6)-2,2-bis(4-hydroxyphenyl)propane.

As the dihydric alcohol, the alkylene oxide adduct of bisphenol A ispreferable. Any of the above dihydric alcohols may be used alone, or twoor more thereof may be used in combination.

A mass average molecular weight of the amorphous polyester resin ispreferably 6×10³ to 18×10³, and more preferably 8×10³ to 14×10³. Whenthe mass average molecular weight of the amorphous polyester resin isequal to or greater than the above-mentioned lower limit, the toner isfurther excellent in low-temperature fixability. When the mass averagemolecular weight of the amorphous polyester resin is equal to or lessthan the above-mentioned upper limit, the toner is also excellent inoffset resistance.

The melting temperature of the amorphous polyester resin is preferably60° C. to 120° C., and more preferably 70° C. to 115° C. When themelting temperature of the amorphous polyester resin is equal to orhigher than the lower limit of the above-mentioned numerical range, thetoner is less likely to be adhered to a roller during fixing. As aresult, the offset resistance at a high temperature is excellent. Thetoner is further excellent in heat resistance. When the meltingtemperature of the amorphous polyester resin is equal to or lower thanthe upper limit of the above-mentioned numerical range, the toner isfurther excellent in low-temperature fixability.

The melting temperature of the amorphous polyester resin can be measuredby, for example, a constant test force extrusion type capillaryrheometer (flowtester).

The other binder resins are obtained by, for example, polymerizing avinyl polymerizable monomer alone or in a plurality of types.

Examples of the vinyl polymerizable monomer include an aromatic vinylmonomer, an ester monomer, a carboxylic acid-containing monomer, and anamine monomer.

Examples of the aromatic vinyl monomer include styrene, methyl styrene,methoxystyrene, phenylstyrene, chlorostyrene, and derivatives thereof.

Examples of the ester monomer include methyl acrylate, ethyl acrylate,butyl acrylate, methyl methacrylate, ethyl methacrylate, butylmethacrylate, and derivatives thereof.

Examples of the carboxylic acid-containing monomer include acrylic acid,methacrylic acid, fumaric acid, maleic acid, and derivatives thereof.

Examples of the amine monomer include aminoacrylate, acrylamide,methacrylamide, vinylpyridine, vinylpyrrolidone, and derivativesthereof.

The other binder resins may be obtained by polycondensation of apolymerizable monomer component formed of an alcohol component and acarboxylic acid component. In polymerization of the polymerizablemonomer component, various auxiliary agents such as a chain transferagent, a crosslinking agent, a polymerization initiator, a surfactant,an aggregating agent, a pH adjusting agent, and an antifoaming agent maybe used.

The ester wax will be described.

The ester wax is formed of two or more types of ester compounds havingdifferent numbers of carbon atoms. Since the toner mother particlecontains the ester wax, the toner is excellent in heat resistance.

The ester wax is a condensation polymer of a first monomer group and asecond monomer group.

The first monomer group will be described.

The first monomer group includes at least three types of carboxylicacids. Therefore, the toner is less likely to aggregate and is excellentin heat resistance. The number of types of carboxylic acids in the firstmonomer group is preferably 7 or less, and more preferably 5 or less,from the viewpoint of easy availability of the ester wax.

A ratio of the carboxylic acid having C_(n) carbon atoms, which is amaximum content, is 70% by mass to 95% by mass, preferably 80% by massto 95% by mass, and more preferably 85% by mass to 95% by mass withrespect to 100% by mass of the first monomer group. Since the ratio ofthe carboxylic acid having C_(n) carbon atoms is equal to or greaterthan the above-mentioned lower limit, a maximum peak in a carbon atomdistribution of the ester wax is located on a sufficiently high carbonatom side. As a result, the toner is excellent in fluidity (conveyanceproperty of developer).

Since the ratio of the carboxylic acid having C_(n) carbon atoms isequal to or less than the above-mentioned upper limit, the toner isexcellent in offset resistance at a low temperature. In addition, theester wax is easily available.

A ratio of a carboxylic acid having 18 or less carbon atoms in the firstmonomer group is 5% by mass or less, preferably 0% by mass to 5% bymass, and more preferably 0% by mass to 1% by mass with respect to 100%by mass of the first monomer group. When the ratio of the carboxylicacid having 18 or less carbon atoms is equal to or greater than theabove-mentioned lower limits, the ester wax is easily available.

Since the ratio of the carboxylic acid having 18 or less carbon atoms isequal to or less than the above-mentioned upper limits, the toner isexcellent in offset resistance at a low temperature.

A content of the carboxylic acid having each number of carbon atoms inthe first monomer group can be measured by, for example, executing massspectrometry by field desorption mass spectrometry (FD-MS) on a productobtained after a methanolysis reaction of the ester wax. A total ionstrength in the carboxylic acid having each number of carbon atoms inthe product obtained by the measurement by FD-MS is defined as 100. Arelative value of the ion strength in the carboxylic acid having eachnumber of carbon atoms with respect to the total ion strength iscalculated. The relative value is defined as the content of thecarboxylic acid having each number of carbon atoms in the first monomergroup. The number of carbon atoms in the carboxylic acid having themaximum relative value is represented by C_(n).

The carboxylic acid in the first monomer group is preferably along-chain carboxylic acid, and more preferably a long-chainalkylcarboxylic acid, from the viewpoint of easy availability of theester wax. The long-chain carboxylic acid is appropriately selected suchthat the ester wax satisfies a predetermined requirement.

The long-chain carboxylic acid is preferably a long-chain carboxylicacid having 19 to 28 carbon atoms, and more preferably a long-chaincarboxylic acid having 20 to 24 carbon atoms. When the number of carbonatoms of the long-chain carboxylic acid is equal to or greater than theabove-mentioned lower limit, the toner is further excellent in heatresistance. When the number of carbon atoms of the long-chain carboxylicacid is equal to or less than the above-mentioned upper limit, the toneris further excellent in low-temperature fixability.

Examples of the long-chain alkylcarboxylic acid include palmitic acid,stearic acid, arachidic acid, behenic acid, lignoceric acid, ceroticacid, and montanic acid.

The second monomer group will be described.

The second monomer group includes at least three types of alcohols.Therefore, the toner is less likely to aggregate and is excellent inheat resistance. The number of types of alcohols in the second monomergroup is preferably 5 or less from the viewpoint of easy availability ofthe ester wax.

A ratio of the alcohol having C_(m) carbon atoms, which is a maximumcontent, is 70% by mass to 90% by mass, preferably 80% by mass to 90% bymass, and more preferably 85% by mass to 90% by mass with respect to100% by mass of the second monomer group. Since the ratio of the alcoholhaving C_(m) carbon atoms is equal to or greater than theabove-mentioned lower limit, a maximum peak in a carbon atomdistribution of the ester wax is located on the sufficiently high carbonatom side. As a result, the toner is excellent in fluidity (conveyanceproperty of developer).

Since the ratio of the alcohol having C_(m) carbon atoms is equal to orless than the above-mentioned upper limit, the toner is excellent inoffset resistance at a low temperature. In addition, the ester wax iseasily available.

A ratio of an alcohol having 18 or less carbon atoms in the secondmonomer group is 20% by mass or less, preferably 10% by mass to 20% bymass, and more preferably 15% by mass to 20% by mass with respect to100% by mass of the second monomer group. When the ratio of the alcoholhaving 18 or less carbon atoms is equal to or greater than theabove-mentioned lower limit, the ester wax is easily available.

Since the ratio of the alcohol having 18 or less carbon atoms is equalto or less than the above-mentioned upper limit, the toner is excellentin offset resistance at a low temperature.

A content of the alcohol having each number of carbon atoms in thesecond monomer group can be measured by, for example, executing massspectrometry by FD-MS on a product obtained after a methanolysisreaction of the ester wax. A total ion strength of the alcohol havingeach number of carbon atoms in the product obtained by the measurementby FD-MS is defined as 100. A relative value of the ion strength of thealcohol having each number of carbon atoms with respect to the total ionstrength is calculated. The relative value is defined as the content ofthe alcohol having each number of carbon atoms in the second monomergroup. The number of carbon atoms in the alcohol having the maximumrelative value is represented by C_(m).

The alcohol in the second monomer group is preferably a long-chainalcohol, and more preferably a long-chain alkyl alcohol, from theviewpoint of easy availability of the ester wax. The long-chain alcoholis appropriately selected such that the ester wax satisfies apredetermined requirement. The long-chain alcohol is preferably along-chain alcohol having 19 to 28 carbon atoms, and more preferably along-chain alcohol having 20 to 22 carbon atoms. When the number ofcarbon atoms of the long-chain alcohol is equal to or greater than theabove-mentioned lower limit, the heat resistance of the ester wax isimproved, and the toner is further excellent in heat resistance. Whenthe number of carbon atoms of the long-chain alcohol is equal to or lessthan the above-mentioned upper limit, the toner is further excellent inlow-temperature fixability.

Examples of the long-chain alkyl alcohol include palmityl alcohol,stearyl alcohol, arachidyl alcohol, behenyl alcohol, lignoceryl alcohol,ceryl alcohol, and montanyl alcohol.

A content of the ester compound having each number of carbon atoms inthe ester wax can be measured by, for example, mass spectrometry byFD-MS. A total ion strength of the ester compound having each number ofcarbon atoms in the ester wax obtained by the measurement by FD-MS isdefined as 100. A relative value of the ion strength of the estercompound having each number of carbon atoms with respect to the totalion strength is calculated. The relative value is defined as the contentof the ester compound having each number of carbon atoms in the esterwax. The number of carbon atoms in the ester compound having the maximumrelative value is represented by C₁.

A method of preparing the ester wax will be described.

The ester wax can be prepared by, for example, subjecting the long-chaincarboxylic acid and the long-chain alcohol to an esterificationreaction. In the esterification reaction, at least three types oflong-chain alkylcarboxylic acids and at least three types of long-chainalkyl alcohols are preferably used from the viewpoint of easilyobtaining an ester wax satisfying the predetermined requirement. Wheneach usage amount of at least three types of long-chain alkylcarboxylicacids and at least three types of long-chain alkyl alcohols is adjusted,the carbon atom distribution of the ester compound contained in theester wax can be adjusted. The esterification reaction is preferablyexecuted while executing heating under a nitrogen stream.

An esterification reaction product may be purified by dissolving theesterification reaction product in a solvent containing ethanol,toluene, or the like, further adding a basic aqueous solution such as asodium hydroxide aqueous solution, and separating the esterificationreaction product into an organic layer and an aqueous layer. The esterwax can be obtained by removing the aqueous layer. The purificationoperation is preferably repeated a plurality of times.

The colorant will be described.

The colorant is not particularly limited. Examples of the colorantinclude carbon black, and pigments and dyes of cyan, yellow, andmagenta.

Examples of the carbon black include aniline black, lamp black,acetylene black, furnace black, thermal black, channel black, and Ketjenblack.

Examples of the pigments and dyes include fast yellow G, benzidineyellow, chrome yellow, quinoline yellow, indofast orange, irgazine red,carmine FB, permanent bordeaux FRR, pigment orange R, lithol red 2G,lake red C, rhodamine FB, rhodamine B Lake, DuPont oil red,phthalocyanine blue, pigment blue, aniline blue, calcoil blue,ultramarine blue, brilliant green B, phthalocyanine green, malachitegreen oxalate, methylene blue chloride, rose bengal, and quinacridone.

Examples of the colorant include, in terms of color index number: C.I.pigment blacks 1, 6, and 7; C.I. pigment yellows 1, 12, 14, 17, 34, 74,83, 97, 155, 180, and 185; C.I. pigment oranges 48 and 49; C.I. pigmentreds 5, 12, 31, 48, 48:1, 48:2, 48:3, 48:4, 48:5, 49, 53, 53:1, 53:2,53:3, 57, 57:1, 81, 81:4, 122, 146, 150, 177, 185, 202, 206, 207, 209,238, and 269; C.I. pigment blues 15, 15:1, 15:2, 15:3, 15:4, 15:5, 15:6,75, 76, and 79; C.I. pigment greens 1, 7, 8, 36, 42, and 58; C.I.pigment violets 1, 19, and 42; and C.I. acid red 52. However, thecolorant is not limited to these exemplified colorants.

Any of the above colorants may be used alone, or two or more thereof maybe used in combination.

The toner mother particle may further contain components other than thebinder resin, the ester wax, and the colorant as long as the effectdisclosed in the embodiment can be exhibited.

Examples of other components include additives such as a charge controlagent, a surfactant, a basic compound, an aggregating agent, a pHadjusting agent, and an antioxidant. However, the additives are notlimited to these exemplified additives. Any of the above additives maybe used alone, or two or more thereof may be used in combination.

The charge control agent will be described.

When the toner mother particle contains the charge control agent, thetoner is easily transferred to a recording medium such as paper.Examples of the charge control agent include a metal-containing azocompound, a metal-containing salicylic acid derivative compound, a metaloxide hydrophobized product, and an inclusion compound of apolysaccharide. As the metal-containing azo compound, a complex or acomplex salt in which the contained metal is iron, cobalt, or chromium,or a mixture of the complex and the complex salt is preferable. As themetal-containing salicylic acid derivative compound and the metal oxidehydrophobized product, a complex or a complex salt in which thecontained metal is zirconium, zinc, chromium, or boron, or a mixture ofthe complex and the complex salt is preferable. As the inclusioncompound of a polysaccharide, an inclusion compound of a polysaccharidecontaining aluminum (Al) and magnesium (Mg) is preferable.

A composition of the toner mother particle will be described.

A content of the crystalline polyester resin is preferably 5% by mass to25% by mass, more preferably 5% by mass to 20% by mass, and still morepreferably 5% by mass to 15% by mass with respect to 100% by mass of thetoner mother particle. When the content of the crystalline polyesterresin is equal to or greater than the above-mentioned lower limit, thetoner is further excellent in low-temperature fixability. When thecontent of the crystalline polyester resin is equal to or less than theabove-mentioned upper limit, the toner is excellent in offsetresistance.

A content of the ester wax is preferably 3% by mass to 15% by mass, morepreferably 3% by mass to 13% by mass, and still more preferably 5% bymass to 10% by mass with respect to 100% by mass of the toner motherparticle. When the content of the ester wax is equal to or greater thanthe above-mentioned lower limit, the toner is further excellent in heatresistance. When the content of the ester wax is equal to or less thanthe above-mentioned upper limit, the toner is further excellent inlow-temperature fixability. In addition, the charge amount is likely tobe sufficiently maintained.

When the toner mother particle contains an amorphous polyester resin, acontent of the amorphous polyester resin is preferably 60% by mass to90% by mass, more preferably 65% by mass to 85% by mass, and still morepreferably 70% by mass to 80% by mass with respect to 100% by mass ofthe toner mother particle. When the content of the amorphous polyesterresin is equal to or greater than the above-mentioned lower limit, thetoner is excellent in offset resistance. When the content of theamorphous polyester resin is equal to or less than the above-mentionedupper limit, the toner is further excellent in low-temperaturefixability.

A content of the colorant is preferably 2% by mass to 13% by mass, andmore preferably 3% by mass to 8% by mass with respect to 100% by mass ofthe toner mother particle. When the content of the colorant is equal toor greater than the above-mentioned lower limit, the toner is excellentin color reproducibility. When the content of the colorant is equal toor less than the above-mentioned upper limit, dispersibility of thecolorant is excellent. In addition, the charge amount of the toner iseasily controlled.

The external additive will be described.

The silica A is usually a secondary particle of silica in which two ormore silica particles are coalesced or aggregated. The secondaryparticle of silica has an indefinite shape. A specific shape of thesecondary particle is not particularly limited. The secondary particlemay have a polygonal columnar shape, a polyhedral shape, or anellipsoidal shape.

On the other hand, the silica B contains single silica particles. Thatis, the silica B is a primary particle of silica. The silica B isadhered to a surface of the toner mother particle in a monodispersedstate. The primary particle of silica means a single particle made ofsilica. The primary particle of silica has preferably a spherical shape,and more preferably a true spherical shape.

The average primary particle diameter D₅₀ of the silica A is a valuemeasured for a composite particle in which two or more silica particlesare coalesced or aggregated. In addition, the average primary particlediameter D₅₀ of the silica B is a value measured for a single silicaparticle.

Since the external additive contains the silica A, the toner accordingto the embodiment has good fluidity and chargeability. The fluidity andchargeability of a recycled toner are also improved.

The average primary particle diameter D₅₀ of the silica A is 10 nm to 14nm, preferably 11 nm to 13 nm, and more preferably 11 nm to 12 nm. Sincethe average primary particle diameter D₅₀ of the silica A is equal to orgreater than the above-mentioned lower limit, the silica A isappropriately and sufficiently adhered to the surface of the tonermother particle. As a result, the silica A can exhibit acharge-imparting effect, and the chargeability of the toner is improved.Therefore, contamination in the machine body due to scattering of therecycled toner is reduced.

Since the average primary particle diameter D₅₀ of the silica A is equalto or less than the above-mentioned upper limit, the silica A is lesslikely to be embedded in the surface of the toner mother particle.Therefore, the toner is excellent in fluidity. Therefore, contaminationin the machine body due to scattering of the recycled toner is reduced.

A content of the silica A is 0.1 parts by mass to 0.8 parts by mass,preferably 0.3 parts by mass to 0.6 parts by mass, and more preferably0.4 parts by mass to 0.5 parts by mass with respect to 100 parts by massof the toner mother particle.

Since the content of the silica A is equal to or greater than theabove-mentioned lower limit, the fluidity of the toner is improved.Therefore, the developer is excellent in conveyance property. Since thechargeability of the toner is improved, the contamination in the machinebody due to scattering of the recycled toner is reduced.

Since the content of the silica A is equal to or less than theabove-mentioned upper limit, the charge amount of the toner is notexcessively high. Therefore, an image density in image formation usingthe recycled toner is sufficiently ensured.

Since the external additive contains the silica B, the external additivecan exhibit a spacing effect between toners. Therefore, the toneraccording to the embodiment is less likely to aggregate and has goodfluidity. In addition, soft caking of the toner is less likely to occur.

The average primary particle diameter D₅₀ of the silica B is 90 nm to150 nm, preferably 100 nm to 140 nm, and more preferably 115 nm to 130nm. Since the average primary particle diameter D₅₀ of the silica B isequal to or greater than the above-mentioned lower limit, the spacingeffect is exhibited. As a result, the toner is less likely to aggregate,and has good heat resistance and fluidity.

Since the average primary particle diameter D₅₀ of the silica B is equalto or less than the above-mentioned upper limit, the improvement of thechargeability by the silica A is hardly inhibited. As a result, thecontamination in the machine body due to scattering of the recycledtoner is reduced.

A content of the silica B is 0.3 parts by mass to 1.2 parts by mass,preferably 0.5 parts by mass to 1.0 part by mass, and more preferably0.7 parts by mass to 0.9 parts by mass with respect to 100 parts by massof the toner mother particle.

Since the content of the silica B is equal to or greater than theabove-mentioned lower limit, the spacing effect is exhibited. As aresult, the toner is less likely to aggregate, and has good heatresistance and fluidity.

Since the content of the silica B is equal to or less than theabove-mentioned upper limit, the improvement of the chargeability by thesilica A is hardly inhibited. As a result, the contamination in themachine body due to scattering of the recycled toner is reduced.

The recycled toner during recycling includes a toner in which anexternal additive is detached from a surface, such as a transferremaining toner or a fogging toner. Since a low-temperature fixing toneris softened at a low temperature, the low-temperature fixing toner islikely to aggregate. Therefore, the fluidity, chargeability, and heatresistance of the low-temperature fixing toner are likely to be reducedas compared with those of general purpose toners. As a result, in imageformation using the recycled toner of the low-temperature fixing toner,contamination in the machine body due to toner scattering and a decreasein image density are likely to occur.

To solve this problem, the toner according to the embodiment containssilica A having a relatively small average primary particle diameterD₅₀. Therefore, the fluidity and the chargeability of the recycled tonerare improved. In addition, the toner according to the embodimentcontains silica B having a relatively large average primary particlediameter D₅₀. Therefore, silica having a relatively large size ispresent on the surface of the toner mother particle. As a result,blocking caused by coalescence of toner particles due to heat or stresscan be prevented. Therefore, the fluidity of the recycled toner and theconveyance property of the developer in a high-temperature environmentare improved.

As described above, in the toner according to the embodiment, since theexternal additive contains two types of silica A and silica B, the tonercharacteristics in a case of recycling are improved.

A ratio of the content of the silica B to the content of the silica A(content of silica B/content of silica A) is 1.0 to 5.0, preferably 1.5to 4.0, and more preferably 2.0 to 3.0. Since the ratio is equal to orgreater than the above-mentioned lower limit, the charge amount of thetoner is not excessively high. Therefore, the image density in the imageformation using the recycled toner is sufficiently ensured.

Since the ratio is equal to or less than the above-mentioned upperlimit, the chargeability of the toner is improved. As a result, thecontamination in the machine body due to scattering of the recycledtoner is reduced.

A total of the content of the silica A and the content of the silica Bis preferably 0.5 parts by mass to 1.7 parts by mass, and morepreferably 0.8 parts by mass to 1.4 parts by mass with respect to 100parts by mass of the toner mother particle. When the total of thecontent of the silica A and the content of the silica B is equal to orgreater than the above-mentioned lower limit, the toner is furtherexcellent in storage stability. When the total of the content of thesilica A and the content of the silica B is equal to or less than theabove-mentioned upper limit, the toner is likely to be sufficientlymelted at the time of fixing.

In the toner according to the embodiment, a residual ratio X of thesilica A is 70% or more, preferably 75% to 100%, and more preferably 85%to 95%. When the residual ratio X is equal to or greater than theabove-mentioned lower limit, the chargeability of the toner is improved.As a result, the contamination in the machine body due to scattering ofthe recycled toner is reduced. When the residual ratio X is equal to orless than the above-mentioned upper limit, the toner is easily produced.

In the toner according to the embodiment, a residual ratio Y of thesilica B is 30% or more, preferably 40% to 90%, and more preferably 50%to 80%. Since the residual ratio Y is equal to or greater than theabove-mentioned lower limit, the spacing effect is exhibited. As aresult, the toner is less likely to aggregate, and has good fluidity.When the residual ratio Y is equal to or less than the above-mentionedupper limit, the toner is easily produced.

A ratio of the residual ratio X to the residual ratio Y (residual ratioX/residual ratio Y) is 1.0 to 3.0, preferably 1.3 to 2.7, and morepreferably 1.6 to 2.4. When the ratio is equal to or greater than theabove-mentioned lower limit, the chargeability of the toner is improved.As a result, the contamination in the machine body due to scattering ofthe recycled toner is reduced.

Since the ratio is equal to or less than the above-mentioned upperlimit, the charge amount of the toner is not excessively high.Therefore, the image density in the image formation using the recycledtoner is sufficiently ensured.

The residual ratio X is calculated according to the following equation(1).

Residual Ratio X=(N _(a2) /N _(a1))×100  Equation (1)

In the equation (1), N_(a1) is the number of adhered silica A measuredfor the toner according to the embodiment, and N_(a2) is the number ofadhered silica A measured for a particle z obtained by the followingmethod Z.

Method Z: executing an ultrasonic treatment on an aqueous liquidcontaining the toner according to the embodiment, water, and asurfactant at 20° C. and 1000 Hz for 10 minutes, then centrifuging theobtained aqueous liquid at 20° C. and 1000 rpm for 15 minutes, removingthe separated external additive, and then executing drying to obtain theparticle z.

The residual ratio Y is calculated according to the following equation(2).

Residual Ratio Y=(N _(b2) /N _(b1))×100  Equation (2)

In the equation (2), N_(b1) is the number of adhered silica B measuredfor the toner according to the embodiment, and N_(b2) is the number ofadhered silica B measured for the particle z obtained by the followingmethod Z.

Method Z: executing an ultrasonic treatment on an aqueous liquidcontaining the toner according to the embodiment, water, and asurfactant at 20° C. and 1000 Hz for 10 minutes, then centrifuging theobtained aqueous liquid at 20° C. and 1000 rpm for 15 minutes, removingthe separated external additive, and then executing drying to obtain theparticle z.

In the equations (1) and (2), N_(a1), N_(a2), N_(b1), and N_(b2) areobtained by counting the number of adhered silica in a scanning electronmicroscope (SEM) image.

In the method Z, it is preferable to stir the aqueous liquid containingthe toner, water, and the surfactant until a toner layer disappearsbefore the aqueous liquid is subjected to the ultrasonic treatment. Thestirring method is not particularly limited. For example, a stirrer canbe used.

In the method Z, when removing the detached external additive, asupernatant in a centrifugal tube is preferably removed by decantation.Thereafter, it is also preferable to further add ion exchange water andrepeat centrifugation and decantation again. The number of repetitiontimes is not particularly limited, and is preferably two.

It can also be said that the particle z obtained by the method Z is adetached toner in which at least a part of the external additive isdetached from the toner according to the embodiment.

The silica A and the silica B are not particularly limited. In general,silica particles can be broadly classified into wet silica and burnedsilica depending on a producing method. The wet silica can be producedby, for example, a method (liquid phase method) of using, as a rawmaterial, sodium silicate, which uses silica sand, neutralizing anaqueous solution containing sodium silicate to precipitate silica, andfiltering and drying the silica. The burned silica (dry silica) isobtained by, for example, reacting silicon tetrachloride in ahigh-temperature flame. The wet silica and the burned silica are bothhydrophobic.

In the silica A and the silica B, a silanol group on the surface of theparticle may be hydrophobized with, for example, silane or silicone. Adegree of hydrophobization of the hydrophobic silica can be measured by,for example, the following method.

Into a beaker, 50 ml of ion exchange water and 0.2 g of a sample arecharged, and methanol is added dropwise from a burette while stirringwith a magnetic stirrer. Next, as a methanol concentration in the beakerincreases, a powder gradually settles, and a percentage by volume of themethanol in a mixed solution of the methanol and the ion exchange waterat the end point at which a total amount of the powder settles isdefined as a degree of hydrophobization (%).

When the external additive is removed from the toner according to theembodiment and a particle diameter distribution is obtained by measuringa particle diameter of the external additive, it is considered that atleast two maximum peaks of silica derived from the silica A and thesilica B are present.

In the particle diameter distribution, it is preferable that at leastone maximum peak, among the at least two maximum peaks, is present ineach of the ranges of 10 nm to 14 nm and 90 nm to 150 nm. In this case,the average primary particle diameter D₅₀ of the silica A can be a modevalue (a modal value) within a range of 10 nm to 14 nm in the particlediameter distribution. The average primary particle diameter D₅₀ of thesilica B can be a mode value (a modal value) within a range of 90 nm to150 nm in the particle diameter distribution.

The particle diameter of each silica particle can be measured by, forexample, a laser diffraction particle size distribution measuringdevice.

However, the external additive may further contain silica other than thesilica A and the silica B as long as the effect disclosed in theembodiment can be exhibited. That is, the external additive may containsilica having an average primary particle diameter D₅₀ of more than 14nm and less than 90 nm within a range in which the effect disclosed inthe embodiment can be exhibited.

The external additive may further contain an inorganic oxide other thanthe silica particle. Examples of other inorganic oxides includestrontium titanate, titanium oxide, alumina, and tin oxide.

The silica particle and particles made of the inorganic oxide may besurface-treated with a hydrophobizing agent from the viewpoint ofimproving stability. Any of the above inorganic oxides may be usedalone, or two or more thereof may be used in combination.

The average primary particle diameter D₅₀ of the toner according to theembodiment is preferably 5.8 μm to 10.0 μm, and more preferably 7.0 μmto 9.0 μm. When the average primary particle diameter D₅₀ of the tonerbased on volume is equal to or greater than the above-mentioned lowerlimit, the toner is further excellent in fluidity. When the averageprimary particle diameter D₅₀ of the toner based on volume is equal toor less than the above-mentioned upper limit, sufficient image densityis easily ensured.

A method of producing the toner will be described.

The toner according to the embodiment can be produced by mixing thetoner mother particle and the external additive. By mixing the tonermother particle and the external additive, the external additive isadhered to the surface of the toner mother particle.

The toner mother particle according to the embodiment can be producedby, for example, a kneading and pulverizing method and a chemicalmethod.

The kneading and pulverizing method will be described.

Examples of the kneading and pulverizing method include a producingmethod including the following mixing step, kneading step, andpulverizing step. The kneading and pulverizing method may furtherinclude the following classifying step as necessary.

Mixing step: a step of mixing at least a crystalline polyester resin, anester wax, and a colorant to obtain a mixture.

-   -   Kneading step: a step of melting and kneading the mixture to        obtain a kneaded product.    -   Pulverizing step: a step of pulverizing the kneaded product to        obtain a pulverized product.    -   Classifying step: a step of classifying the pulverized product.

In the mixing step, raw materials of the toner are mixed to obtain themixture. In the mixing step, a mixer may be used. The mixer is notparticularly limited. In the mixing step, another binder resin andanother additive may be used as necessary.

In the kneading step, the mixture obtained in the mixing step is meltedand kneaded to obtain the kneaded product. In the kneading step, akneader may be used. The kneader is not particularly limited.

In the pulverizing step, the kneaded product obtained in the kneadingstep is pulverized to obtain the pulverized product. In the pulverizingstep, a pulverizer may be used. As the pulverizer, various pulverizerssuch as a hammer mill can be used. The pulverized product obtained bythe pulverizer may be further finely pulverized. Various pulverizers canbe used for further finely pulverizing the pulverized product. Thepulverized product obtained in the pulverizing step may be used as thetoner mother particle as it is, or may be used as the toner motherparticle through the classifying step as necessary.

In the classifying step, the pulverized product obtained in thepulverizing step is classified. In the classifying step, a classifiermay be used. The classifier is not particularly limited.

The chemical method will be described.

In the chemical method, a mixture is obtained by mixing a crystallinepolyester resin, an ester wax, a colorant, and if necessary, anotherbinder resin and another additive. Next, the mixture is melted andkneaded to obtain a kneaded product. Next, the kneaded product ispulverized to obtain roughly granulated medium-sized particles. Next,the medium-sized particles are mixed with an aqueous medium to prepare amixed liquid. Next, the mixed liquid is subjected to mechanical shearingto obtain a fine particle dispersion liquid. Finally, fine particles areaggregated in the fine particle dispersion liquid to obtain a tonermother particle.

A method of adding the external additive will be described (externaladdition step).

The external additive is stirred with the toner mother particle by, forexample, a mixer. The mixer preferably has a temperature controlfunction. A temperature at which the external additive is adhered to thetoner mother particle is not particularly limited, and is preferably 15°C. to 30° C., for example. As the temperature at which the externaladditive is adhered to the toner mother particle is higher, the silica Aand the silica B are more likely to be adhered to the toner motherparticle. Therefore, the residual ratio X and the residual ratio Y arelikely to increase.

An order of adhering the silica A and the silica B is not particularlylimited. That is, the silica B may be adhered after the silica A isadhered, the silica A may be adhered after the silica B is adhered, orthe silica A and the silica B may be adhered at the same time bystirring.

A stirring speed at which the silica A and the silica B are adhered tothe toner mother particle is not particularly limited. The stirringspeed is appropriately set according to a scale of a productionfacility. In a case of a laboratory scale stirrer, for example, 2000 rpmto 3000 rpm is preferable. As the stirring speed at which the externaladditive is adhered to the toner mother particle is higher, the silica Aand the silica B are more likely to be adhered to the toner motherparticle. Therefore, the residual ratio X and the residual ratio Y arelikely to increase.

A stirring time of the silica A and the silica B is preferably 180seconds to 480 seconds. When the stirring time of the silica A and thesilica B is within the above-mentioned numerical range, the silica A andthe silica B are likely to be adhered to the toner mother particle.Therefore, the residual ratio X and the residual ratio Y are likely toincrease.

The external additive before stirring may be sieved by a sieving deviceas necessary. The sieving device is not particularly limited. Varioussieving devices can be used.

A toner cartridge according to the embodiment will be described.

The toner cartridge according to the embodiment accommodates the toneraccording to the embodiment described above. For example, the tonercartridge includes a container, and the toner according to theembodiment is accommodated in the container. The container is notparticularly limited, and various containers applicable to an imageforming apparatus can be used.

The toner according to the embodiment may be used as a one-componentdeveloper, or may be used as a two-component developer in combinationwith a carrier.

Hereinafter, an image forming apparatus according to the embodiment willbe described with reference to the drawings. FIG. 1 is a diagramillustrating an example of a schematic structure of an image formingapparatus capable of recycling a collected toner.

A copying machine main body 101 illustrated in FIG. 1 includes: an imageforming unit 101A provided at one side of a central portion; a documentplacing table 135 provided at an upper surface portion; a scanner 136provided at a lower side of the document placing table 135; and aplurality of stages of sheet feeding cassettes 142 and 143 provided at alower side.

The image forming unit 101A includes: a photoconductor drum 102 that isrotatable in an arrow direction; a charger 103 that charges a surface ofthe photoconductor drum 102; a laser unit 104 that forms anelectrostatic latent image on the surface of the photoconductor drum102; a developing device 105 that develops the electrostatic latentimage on the photoconductor drum 102 with a toner; a transfer charger106 that transfers a toner image on the photoconductor drum 102 to asheet; a cleaning device 107 that removes the remaining toner on thephotoconductor drum 102; and a replenishing container 108 that isprovided above the developing device 105.

The charger 103, the laser unit 104, the developing device 105, thetransfer charger 106, and the cleaning device 107 are provided aroundthe photoconductor drum 102 in this order along a rotation direction ofthe photoconductor drum 102.

The replenishing container 108 replenishes the toner according to theembodiment to the developing device 105. The toner according to theembodiment is stored in the replenishing container 108.

The scanner 136 exposes a document on the document placing table 135.The scanner 136 includes: a light source 137 that irradiates thedocument with light; a first reflection mirror 138 that reflects thelight reflected from the document in a predetermined direction; a secondreflection mirror 139 and a third reflection mirror 140 thatsequentially reflect the light reflected from the first reflectionmirror 138; and a light receiving element 141 that receives the lightreflected from the third reflection mirror 140.

The sheet feeding cassettes 142 and 143 feed out the sheet to the imageforming unit 101A. The sheet is conveyed upward via a conveyance system144. The conveyance system 144 includes a conveyance roller pair 145, aregistration roller pair 146, the transfer charger 106, a fixing rollerpair 147, and a sheet discharge roller pair 148.

In the image forming apparatus illustrated in FIG. 1 , for example,image formation is executed as follows.

First, a document on the document placing table 135 is irradiated withlight from the light source 137. The irradiation light is reflected fromthe document, passes through the first reflection mirror 138, the secondreflection mirror 139, and the third reflection mirror 140 in thisorder, and is received by the light receiving element 141, so that adocument image is read. Next, based on read information of the lightreceiving element 141, the laser unit 104 irradiates the surface of thephotoconductor drum 102 with a laser beam LB.

Here, the surface of the photoconductor drum 102 is negatively chargedby the charger 103. When the laser beam LB is emitted from the laserunit 104, the photoconductor drum 102 is exposed, and a potential of theirradiated portion approaches 0. Therefore, in a region corresponding toan image portion of the document, a surface potential of thephotoconductor drum 102 approaches 0 according to a density of theimage, and an electrostatic latent image is formed.

The electrostatic latent image becomes a toner image by adsorbing thetoner at a position facing the developing device 105 by a rotation ofthe photoconductor drum 102. When a toner image is to be formed, a sheetis supplied from the sheet feeding cassettes 142 and 143 to theconveyance system 144. The sheet is aligned by the registration rollerpair 146, and then is fed between the transfer charger 106 and thephotoconductor drum 102. Thereafter, the toner image on thephotoconductor drum 102 is transferred onto the sheet.

The sheet to which the toner image is transferred is conveyed to thefixing roller pair 147. In the fixing roller pair 147, the sheet ispressurized and heated, and the toner image is fixed to the sheet. Thetoner according to the embodiment is excellent in low-temperaturefixability. Therefore, fixing can be executed at, for example, about140° C. to 170° C. After the fixing, the sheet is discharged onto asheet discharge tray 150 via the sheet discharge roller pair 148.

On the other hand, the toner remaining on the surface of thephotoconductor drum 102 without being transferred to the sheet isremoved by the cleaning device 107. Thereafter, the toner is returned tothe developing device 105 by a collecting mechanism 110 and recycled. Inthe image forming apparatus illustrated in FIG. 1 , when the toner inthe developing device 105 is consumed, the toner according to theembodiment is newly replenished as a fresh toner from the replenishingcontainer 108.

The developing device 105 will be described with reference to FIGS. 2and 3 .

The developing device 105 includes: the collecting mechanism 110 thatcollects the toner for recycling; a developing container 111 in whichthe developer containing the toner according to the embodiment isstored; a developing roller 112 that is rotatably provided in thedeveloping container 111; a first partition wall 114 and a secondpartition wall 115 that form a first chamber 116, a second chamber 117,and a third chamber 118 in the developing container 111; a first mixer120 that is provided in the first chamber 116; a second mixer 121 thatis provided in the second chamber 117; a third mixer 122 that isprovided in the third chamber 118; a fresh toner receiving unit 123 thatreceives the fresh toner supplied from the replenishing container; arecycled toner receiving unit 124; and a toner concentration detector129.

The developing device 105 is connected to the cleaning device 107 viathe collecting mechanism 110. In the developing device 105, thecollecting mechanism 110 is an auger to which the toner for recycling isconveyed. However, the collecting mechanism 110 is not limited to theauger.

The cleaning device 107 may be a cleaning blade or a cleaning brush.

The developing roller 112 is disposed at a position facing a lowersurface portion of the photoconductor drum. The developing roller 112supplies the developer to the photoconductor drum by rotating.

A first communication portion 125 is formed on a first end portion sideof the first partition wall 114. A second communication portion 126 isformed on a second end portion side of the first partition wall 114. Athird communication portion 127 and a fourth communication portion 128are formed in the second partition wall 115.

The inside of the developing container 111 is partitioned into the firstchamber 116, the second chamber 117, and the third chamber 118 by thefirst partition wall 114 and the second partition wall 115. The firstchamber 116, the second chamber 117, and the third chamber 118 areformed substantially parallel to each other along an axial direction ofthe photoconductor drum 102.

Here, on a sheet surface, in the first partition wall 114, a directionfrom the second communication portion 126 toward the first communicationportion 125 is referred to as a first direction. A direction opposite tothe first direction, that is, a direction from the first communicationportion 125 toward the second communication portion 126 is referred toas a second direction.

By rotation, the first mixer 120 stirs and conveys the developer in thefirst direction and supplies the developer to the developing roller 112.The second mixer 121 and the third mixer 122 stir and convey thedeveloper in the second direction and feed the developer to an upstreamside of the first mixer 120.

The second mixer 121 and the third mixer 122 are rotationally driven bya driving unit. In the developing device 105, the driving unit includes:a driving motor 162 as a single driving source; and a driving gear 163rotated by the driving motor 162. A rotary shaft 151 of the third mixer122 is connected to the driving gear 163 via a large-diameter powertransmission gear 164. A rotation shaft 121 a of the second mixer 121 isconnected to the large-diameter power transmission gear 164 via asmall-diameter power transmission gear 165.

In the developing device 105 having the above-described configuration, aspeed of conveying the developer by the third mixer 122 is lower than aspeed of conveying the developer by the second mixer 121. Therefore, atime of conveying the developer by the third mixer 122 is longer than atime of conveying the developer by the second mixer 121.

Here, in another embodiment, the second mixer 121 and the third mixer122 may be individually rotationally driven by a plurality of drivingmotors having different rotation speeds. The third mixer 122 may beprovided with a reverse feed blade that conveys the collected toner in adirection opposite to the second direction. In either method, a speed ofconveying the collected toner by the third mixer 122 can be made lowerthan the speed of conveying the developer by the second mixer 121.

Next, a developing operation of the developing device 105 will bedescribed with reference to FIGS. 2 and 3 .

In the developing container 111, the developer is stirred and conveyedin the first direction by a rotation of the first mixer 120, and issupplied to the developing roller 112. Thereafter, the developer issupplied to the electrostatic latent image on the photoconductor drum102 by a rotation of the developing roller 112, and the electrostaticlatent image is visualized.

The developer conveyed out from the first mixer 120 is guided into thesecond chamber 117 through the first communication portion 125.Thereafter, in the second chamber 117, the developer is conveyed in anarrow direction (the second direction) by a rotation of the second mixer121. The developer conveyed out by the second mixer 121 is fed out tothe upstream side of the first mixer 120 through the secondcommunication portion 126, and is conveyed so as to circulate betweenthe first mixer 120 and the second mixer 121.

A part of the developer conveyed by the second mixer 121 is fed into thethird chamber 118 through the third communication portion 127 andconveyed in the arrow direction (the second direction). The developer isfed again into the second chamber 117 through the fourth communicationportion 128, and is stirred and conveyed by the second mixer 121.Thereafter, the developer is fed to the upstream side of the first mixer120 through the second communication portion 126.

Here, a toner concentration of the developer stirred and conveyed by thesecond mixer 121 is detected by the toner concentration detector 129.When the toner concentration detected by the toner concentrationdetector 129 is equal to or less than a predetermined value, the toneraccording to the embodiment is replenished from the replenishingcontainer 108. The toner falls into the fresh toner receiving unit 123of the developing container 111. The fresh toner is stirred and conveyedin the arrow direction (the second direction) by the rotation of thesecond mixer 121, and is fed to the upstream side of the first mixer120.

The collected toner collected from the cleaning device 107 by thecollecting mechanism 110 falls into the recycled toner receiving unit124. The collected toner is conveyed in the second direction by arotation of the third mixer 122. Here, the developer guided through thethird communication portion 127 into the third chamber 118 is stirredand conveyed toward the recycled toner receiving unit 124 as indicatedby an arrow a by a rotation of a reverse feed blade 153 of the thirdmixer 122. Thereafter, the developer is stirred and conveyed togetherwith the collected toner in the second direction as indicated by anarrow b by a rotation of a forward feed blade 152. The collected toneris fed to the upstream side of the first mixer 120 through the fourthcommunication portion 128 and the second communication portion 126 inthis order.

The developer and the collected toner may be fed to a downstream side ina conveyance direction without being fed into the second chamber 117through the fourth communication portion 128. Such developer andcollected toner are reversely fed by a rotation of a reverse feed blade155, returned to the fourth communication portion 128, and fed to thesecond chamber 117 through the fourth communication portion 128.

In the related art, when a developer containing a toner is recycled, anexternal additive is easily peeled off from a toner mother particle dueto physical stress, and soft caking is remarkably generated. Therefore,there is a problem in that the conveyance property of the developer isreduced, and the charge amount and the scattering amount of the tonerare reduced.

In contrast, the toner according to the embodiment is excellent instorage stability in a high-temperature environment even when recycled,and is capable of sufficiently maintaining the charge amount. Therefore,the charge amount and the scattering amount of the toner aresufficiently maintained, and good development is executed.

FIG. 4 illustrates an example of an image forming apparatus to which thedeveloper containing the toner according to the embodiment is applied.

The image forming apparatus illustrated in FIG. 4 is in a form in whicha toner image is fixed. However, the image forming apparatus accordingto the embodiment is not limited to this form. An image formingapparatus according to another embodiment may be, for example, in a formof an inkjet image forming apparatus.

An image forming apparatus 1 illustrated in FIG. 4 is a four-drum tandemcolor copier MFP. The image forming apparatus 1 includes: a scanner unit2; a sheet discharge unit 3; a sheet feeding cassette 4; an intermediatetransfer belt 10; four image forming stations 11Y, 11M, 11C, and 11Kdisposed along a traveling direction S of the intermediate transfer belt10; a secondary transfer roller 27; a fixing device 30; and a manualfeed mechanism 31.

The intermediate transfer belt 10 is wound around and supported by adriven roller 20 and a backup roller 21. Any tension is applied to theintermediate transfer belt 10 by a first tension roller 22, a secondtension roller 23, and a third tension roller 24 in addition to thedriven roller 20 and the backup roller 21.

The image forming stations 11Y, 11M, 11C, and 11K respectively havephotoconductor drums 12Y, 12M, 12C, and 12K that are in contact with theintermediate transfer belt 10.

Around the photoconductor drums 12Y, 12M, 12C, and 12K, chargers 13Y,13M, 13C, and 13K, developing devices 14Y, 14M, 14C, and 14K,photoconductor cleaning devices 16Y, 16M, 16C, and 16K, and primarytransfer rollers 18Y, 18M, 18C, and 18K are disposed.

The chargers 13Y, 13M, 13C, and 13K negatively charge surfaces of thephotoconductor drums 12Y, 12M, 12C, and 12K. Between the chargers 13Y,13M, 13C, and 13K and the developing devices 14Y, 14M, 14C, and 14K, alaser exposure device 17 irradiates the photoconductor drums 12Y, 12M,12C, and 12K with exposure light. Electrostatic latent images are formedon the photoconductor drums 12Y, 12M, 12C, and 12K.

The developing devices 14Y, 14M, 14C, and 14K respectively have atwo-component developer containing toners of yellow (Y), magenta (M),cyan (C), and black (K) and a carrier. The developing devices 14Y, 14M,14C, and 14K respectively supply a toner to the electrostatic latentimages on the photoconductor drums 12Y, 12M, 12C, and 12K. In this way,the image forming stations 11Y, 11M, 11C, and 11K respectively formsingle-color images of yellow (Y), magenta (M), cyan (C), and black (K).

The primary transfer rollers 18Y, 18M, 18C, and 18K are provided on theintermediate transfer belt 10 at positions facing the photoconductordrums 12Y, 12M, 12C, and 12K, respectively. The primary transfer rollers18Y, 18M, 18C, and 18K primarily transfer toner images on thephotoconductor drums 12Y, 12M, 12C, and 12K to the intermediate transferbelt 10.

The primary transfer rollers 18Y, 18M, 18C, and 18K are conductiverollers. A primary transfer bias voltage is applied to each of theprimary transfer rollers 18Y, 18M, 18C, and 18K.

The secondary transfer roller 27 is disposed at a transfer positionwhere the intermediate transfer belt 10 is supported by the backuproller 21. The backup roller 21 is a conductive roller. A predeterminedsecondary transfer bias is applied to the backup roller 21.

When sheet paper as a printing object passes between the intermediatetransfer belt 10 and the secondary transfer roller 27, the toner imageon the intermediate transfer belt 10 is secondarily transferred onto thesheet paper. After completion of the secondary transfer, theintermediate transfer belt 10 is cleaned by a belt cleaner 10 a.

The sheet feeding cassette 4 is provided below the laser exposure device17. The sheet feeding cassette 4 supplies sheet paper P1 toward thesecondary transfer roller 27. A pickup roller 4 a, a separation roller28 a, a conveyance roller 28 b, and a registration roller pair 36 areprovided between the sheet feeding cassette 4 and the secondary transferroller 27.

The manual feed mechanism 31 is provided on one side surface portion ofthe image forming apparatus 1. The manual feed mechanism 31 is formanually feeding sheet paper P2. In the manual feed mechanism 31, amanual pickup roller 31 b and a manual separation roller 31 c areprovided between a manual feed tray 31 a and the registration rollerpair 36.

A media sensor 39 that detects a type of the sheet paper is disposed ona vertical conveyance path 35 through which the sheet paper is conveyedfrom the sheet feeding cassette 4 or the manual feed tray 31 a. Theimage forming apparatus 1 can control a conveyance speed, a transfercondition, a fixing condition, and the like of the sheet paper based ona detection result obtained by the media sensor 39. The sheet paper isconveyed along the vertical conveyance path 35 to the fixing device 30via the registration roller pair 36 and the secondary transfer roller27.

The fixing device 30 includes: a fixing belt 53 wound around a pair of aheating roller 51 and a driving roller 52; and a counter roller 54disposed to face the heating roller 51 via the fixing belt 53. Thefixing device 30 can heat a portion of the fixing belt 53 that is incontact with the heating roller 51. The fixing device 30 applies heatand pressure to the sheet paper on which the toner image is transferredbetween the fixing belt 53 and the counter roller 54, and fixes thetoner image to the sheet paper.

The toner according to the embodiment is excellent in low-temperaturefixability. Therefore, fixing can be executed at, for example, about140° C. to 170° C.

A gate 33 is provided downstream of the fixing device 30. The sheetpaper is distributed in a direction of a sheet discharge roller 41 or ina direction of a re-conveyance unit 32. The sheet paper distributed tothe sheet discharge roller 41 is discharged to the sheet discharge unit3. On the other hand, the sheet paper distributed to the re-conveyanceunit 32 is guided toward the secondary transfer roller 27 again.

In the image forming apparatus 1 illustrated in FIG. 4 , the imageforming station 11Y includes the photoconductor drum 12Y and a processmember integrally with each other, and is detachably adhered to a mainbody of the image forming apparatus. Examples of the process memberinclude the charger 13Y, the developing device 14Y, and thephotoconductor cleaning device 16Y. However, in another embodiment, eachof the image forming stations 11Y, 11M, 11C, and 11K may be detachablyadhered to the image forming apparatus, or may be detachably adhered tothe image forming apparatus as an integrated image forming unit 11.

The toner according to the embodiment may be applied to an image formingapparatus in which the developing device 14Y of the image formingapparatus illustrated in FIG. 4 is modified. FIG. 5 illustrates anexample of a modification of the developing device applicable to theimage forming apparatus illustrated in FIG. 4 .

A developing device 64Y illustrated in FIG. 5 accommodates atwo-component developer containing a yellow toner and a carrier. Thedeveloping device 64Y includes a toner concentration sensor Q. The tonerconcentration sensor Q detects a decrease in toner concentration. Whenthe developing device 64Y detects a decrease in concentration, thedeveloping device 64Y replenishes the yellow toner from a tonercartridge (not illustrated). In this way, the developing device 64Y canmaintain a toner concentration constant.

In addition, the developing device 64Y can replenish the carrier fromthe toner cartridge (not illustrated) through a developer replenishingport 64Y1. The developing device 64Y can discharge the developer from adeveloper discharge port 64Y2 through overflow by an amount to bereplenished.

In this way, in the developing device 64Y, an amount of the developer ismaintained constant, and an old deteriorated carrier is replaced with anew carrier little by little.

Similar to the developing device 14Y, the developing devices 14M, 14C,and 14K in FIG. 4 may be respectively modified into developing devices64M, 64C, and 64K (not illustrated) similar to the developing device 64Yexcept that a magenta toner, a cyan toner, and a black toner arerespectively used instead of the yellow toner.

The toner according to at least one embodiment described above isexcellent in low-temperature fixability, excellent in storage stabilityin a high-temperature environment even when recycled, and is capable ofsufficiently maintaining the charge amount.

Examples

Hereinafter, the embodiment will be described in more detail by means ofExamples.

Preparations of ester waxes A1 to A12 and B1 to B8 in Examples will bedescribed.

A four-necked flask equipped with a stirrer, a thermocouple, and anitrogen inlet tube was charged with 80 parts by mass of at least threetypes of long-chain alkylcarboxylic acids and 20 parts by mass of atleast three types of long-chain alkyl alcohols. An esterificationreaction was executed at 220° C. under a nitrogen stream to obtain areaction product. A mixed solvent of toluene and ethanol was added tothe obtained reaction product to dissolve the reaction product. Further,a sodium hydroxide aqueous solution was added to the flask, and themixture was stirred at 70° C. for 30 minutes. Further, the flask wasallowed to stand for 30 minutes to separate the content in the flaskinto an organic layer and an aqueous layer, and the aqueous layer wasremoved from the content. Thereafter, ion exchange water was added tothe flask, and the mixture was stirred at 70° C. for 30 minutes. Theflask was allowed to stand for 30 minutes to separate the content in theflask into an aqueous layer and an organic layer, and the aqueous layerwas removed from the content. The operation was repeated five times. Thesolvent was distilled off from the organic layer of the content in theflask under a reduced pressure to obtain an ester wax A1.

Ester waxes A2 to A12 were obtained in the same manner as the ester waxA1 except that types and usage amounts of the long-chain alkylcarboxylicacids and the long-chain alkyl alcohols used were changed. Ester waxesB1 to B8 were obtained by the same operation.

The long-chain alkylcarboxylic acids used are as follows.

-   -   Palmitic acid (C₁₆H₃₂O₂)    -   Stearic acid (C₁₈H₃₆O₂)    -   Arachidic acid (C₂₀H₄₀O₂)    -   Behenic acid (C₂₂H₄₄O₂)    -   Lignoceric acid (C₂₄H₄₈O₂)    -   Cerotic acid (C₂₆H₅₂O₂)    -   Montanic acid (C₂₈H₅₆O₂)

The long-chain alkyl alcohols used are as follows.

-   -   Palmityl alcohol (C₁₆H₃₄O)    -   Stearyl alcohol (C₁₈H₃₈O)    -   Arachidyl alcohol (C₂₀H₄₂O)    -   Behenyl alcohol (C₂₂H₄₆O)    -   Lignoceryl alcohol (C₂₄H₅₀O)    -   Ceryl alcohol (C₂₆H₅₄O)    -   Montanyl alcohol (C₂₈H₅₈O)

A toner according to Example 1 was produced as follows.

First, raw materials of a toner mother particle were charged into aHenschel mixer (manufactured by Mitsui Mining Co., Ltd.) and mixed.Further, a mixture of the raw materials of the toner mother particle wasmelted and kneaded by a twin-screw extruder. The melt-kneaded productwas cooled and then coarsely pulverized with a hammer mill. The coarselypulverized product was finely pulverized by a jet pulverizer. The finelypulverized product was classified to obtain the toner mother particle.

The composition of the raw materials of the toner mother particle isshown below.

Crystalline polyester resin: 5 parts by mass

Amorphous polyester resin: 85 parts by mass

Ester wax A1: 5 parts by mass

Carbon black: 4.5 parts by mass

Charge control agent: 0.5 parts by mass

Next, the temperature in the Herschel mixer having a temperature controlfunction is set to 25° C. After the toner mother particle was chargedinto a stirring unit, 0.5 parts by mass of titanium oxide was chargedwith respect to 100 parts by mass of the toner mother particle, and themixture was stirred at 25° C. and 2500 rpm for 6 minutes. Thereafter,the stirring was stopped, 0.45 parts by mass of the silica A withrespect to 100 parts by mass of the toner mother particle was added tothe stirring unit, and the mixture was stirred at 25° C. and 2500 rpmfor 360 seconds. The stirring was stopped again, 0.75 parts by mass ofthe silica B with respect to 100 parts by mass of the toner motherparticle and other necessary external additives were added to thestirring unit, and the mixture was further stirred at 25° C. and 2500rpm for 360 seconds to obtain the toner according to Example 1.

Toners according to Examples 2 to 23 and Comparative Examples 1 to 22were produced as follows.

First, toner mother particles of Examples 2 to 23 and ComparativeExamples 1 to 22 were produced in the same manner as in Example 1 exceptthat ester waxes A2 to A12 and B1 to B8 were used in place of the esterwax A1 as shown in Tables 1, 2, 3, and 4 with respect to the compositionof the raw materials of the toner mother particle.

Next, the external additive was mixed with the toner mother particle ineach Example to produce the toners according to Examples 2 to 23 andComparative Examples 1 to 22 in the same manner as in Example 1 exceptthat an average primary particle diameter D₅₀ (r_(A)) of the silica A,an average primary particle diameter D₅₀ (r_(B)) of the silica B, acontent w_(A) of the silica A, and a content w_(B) of the silica B werechanged as shown in Tables 1, 2, 3, and 4, and external additionconditions of the silica A and the silica B were changed as shown inTables 5, 6, 7, and 8.

TABLE 1 w_(A) w_(B) Residual Residual r_(A) r_(B) (part by (part byratio X ratio Y Ester wax (nm) (nm) mass) mass) w_(B)/w_(A) (%) (%)Example 1 Ester wax A1 12 120 0.45 0.75 1.7 85.0 50.0 Example 2 Esterwax A2 12 120 0.45 0.75 1.7 85.0 50.0 Example 3 Ester wax A3 12 120 0.450.75 1.7 85.0 50.0 Example 4 Ester wax A4 12 120 0.45 0.75 1.7 85.0 50.0Example 5 Ester wax A5 12 120 0.45 0.75 1.7 85.0 50.0 Example 6 Esterwax A6 12 120 0.45 0.75 1.7 85.0 50.0 Example 7 Ester wax A7 12 120 0.450.75 1.7 85.0 50.0 Example 8 Ester wax A8 12 120 0.45 0.75 1.7 85.0 50.0Example 9 Ester wax A9 12 120 0.45 0.75 1.7 85.0 50.0 Example 10 Esterwax A10 12 120 0.45 0.75 1.7 85.0 50.0 Example 11 Ester wax A11 10 1200.45 0.75 1.7 85.0 50.0 Example 12 Ester wax A11 14 120 0.45 0.75 1.785.0 50.0 Ratio of Low- residual temperature Heat Conveyance Toner Imageratios X/Y fixability resistance property scattering density Example 11.7 Good Good Good Good Good Example 2 1.7 Good Good Good Good GoodExample 3 1.7 Good Good Good Good Good Example 4 1.7 Good Good Good GoodGood Example 5 1.7 Good Good Good Good Good Example 6 1.7 Good Good GoodGood Good Example 7 1.7 Good Good Good Good Good Example 8 1.7 Good GoodGood Good Good Example 9 1.7 Good Good Good Good Good Example 10 1.7Good Good Good Good Good Example 11 1.7 Good Good Good Good Good Example12 1.7 Good Good Good Good Good

TABLE 2 w_(A) w_(B) Residual Residual r_(A) r_(B) (part by (part byratio X ratio Y Ester wax (nm) (nm) mass) mass) w_(B)/w_(A) (%) (%)Example 13 Ester wax A11 12 90 0.45 0.75 1.7 85.0 50.0 Example 14 Esterwax A11 12 150 0.45 0.75 1.7 85.0 50.0 Example 15 Ester wax A11 12 1200.1 0.5 5.0 85.0 50.0 Example 16 Ester wax A11 12 120 0.8 0.8 1.0 85.050.0 Example 17 Ester wax A12 12 120 0.3 0.3 1.0 85.0 50.0 Example 18Ester wax A12 12 120 0.24 1.2 5.0 85.0 50.0 Example 19 Ester wax A12 12120 0.45 0.75 1.7 70.0 50.0 Example 20 Ester wax A12 12 120 0.45 0.751.7 85.0 30.0 Example 21 Ester wax A12 12 120 0.45 0.75 1.7 70.0 70.0Example 22 Ester wax A12 12 120 0.45 0.75 1.7 90.0 30.0 Example 23 Esterwax A12 12 120 0.45 0.75 1.7 90.0 90.0 Ratio of Low- residualtemperature Heat Conveyance Toner Image ratios X/Y fixability resistanceproperty scattering density Example 13 1.7 Good Good Good Good GoodExample 14 1.7 Good Good Good Good Good Example 15 1.7 Good Good GoodGood Good Example 16 1.7 Good Good Good Good Good Example 17 1.7 GoodGood Good Good Good Example 18 1.7 Good Good Good Good Good Example 191.4 Good Good Good Good Good Example 20 2.8 Good Good Good Good GoodExample 21 1.0 Good Good Good Good Good Example 22 3.0 Good Good GoodGood Good Example 23 1.0 Good Good Good Good Good

TABLE 3 wA wB Residual Residual rA rB (part by (part by ratio X ratio YEster wax (nm) (nm) mass) mass) wB/wA (%) (%) Comparative Ester wax B112 120 0.45 0.75 1.7 85.0 50.0 Example 1 Comparative Ester wax B2 12 1200.45 0.75 1.7 85.0 50.0 Example 2 Comparative Ester wax B3 12 120 0.450.75 1.7 85.0 50.0 Example 3 Comparative Ester wax B4 12 120 0.45 0.751.7 85.0 50.0 Example 4 Comparative Ester wax B5 12 120 0.45 0.75 1.785.0 50.0 Example 5 Comparative Ester wax B6 12 120 0.45 0.75 1.7 85.050.0 Example 6 Comparative Ester wax B7 12 120 0.45 0.75 1.7 85.0 50.0Example 7 Comparative Ester wax B8 12 120 0.45 0.75 1.7 85.0 50.0Example 8 Comparative Ester wax A12 9 120 0.45 0.75 1.7 85.0 50.0Example 9 Comparative Ester wax A12 15 120 0.45 0.75 1.7 85.0 50.0Example 10 Comparative Ester wax A12 12 89 0.45 0.75 1.7 85.0 50.0Example 11 Ratio of Low- residual temperature Heat Conveyance TonerImage ratios X/Y fixability resistance property scattering densityComparative 1.7 Poor Good Good Good Good Example 1 Comparative 1.7 PoorGood Good Good Good Example 2 Comparative 1.7 Good Poor Good Good GoodExample 3 Comparative 1.7 Good Poor Good Good Good Example 4 Comparative1.7 Good Good Poor Good Good Example 5 Comparative 1.7 Poor Good GoodGood Good Example 6 Comparative 1.7 Good Good Poor Good Good Example 7Comparative 1.7 Poor Good Good Good Good Example 8 Comparative 1.7 GoodGood Good Poor Good Example 9 Comparative 1.7 Good Good Good Poor GoodExample 10 Comparative 1.7 Good Poor Poor Good Good Example 11

TABLE 4 w_(A) w_(B) Residual Residual r_(A) r_(B) (part by (part byratio X ratio Y Ester wax (nm) (nm) mass) mass) w_(B)/w_(A) (%) (%)Comparative Ester wax A12 12 151 0.45 0.75 1.7 85.0 50.0 Example 12Comparative Ester wax A12 12 120 0.05 0.75 15.0 85.0 50.0 Example 13Comparative Ester wax A12 12 120 0.9 0.75 0.8 85.0 50.0 Example 14Comparative Ester wax A12 12 120 0.45 0.2 0.4 85.0 50.0 Example 15Comparative Ester wax A12 12 120 0.45 1.3 2.9 85.0 50.0 Example 16Comparative Ester wax A12 12 120 0.8 0.75 0.9 85.0 50.0 Example 17Comparative Ester wax A12 12 120 0.23 1.2 5.2 85.0 50.0 Example 18Comparative Ester wax A12 12 120 0.45 0.75 1.7 69.0 50.0 Example 19Comparative Ester wax A12 12 120 0.45 0.75 1.7 85.0 29.0 Example 20Comparative Ester wax A12 12 120 0.45 0.75 1.7 70.0 75.0 Example 21Comparative Ester wax A12 12 120 0.45 0.75 1.7 95.0 30.0 Example 22Ratio of Low- residual temperature Heat Conveyance Toner Image ratiosX/Y fixability resistance property scattering density Comparative 1.7Good Good Good Poor Good Example 12 Comparative 1.7 Good Good Poor PoorGood Example 13 Comparative 1.7 Good Good Good Good Poor Example 14Comparative 1.7 Good Poor Poor Good Good Example 15 Comparative 1.7 GoodGood Good Poor Good Example 16 Comparative 1.7 Good Good Good Good PoorExample 17 Comparative 1.7 Good Good Good Poor Good Example 18Comparative 1.4 Good Good Good Poor Good Example 19 Comparative 2.9 GoodGood Poor Good Good Example 20 Comparative 0.9 Good Good Good Poor GoodExample 21 Comparative 3.2 Good Good Good Good Poor Example 22

TABLE 5 Addition of silica A Addition of silica B (first step) (secondstep) Rotation Stirring Rotation Stirring speed time Temperature speedtime Temperature (rpm) (s) (° C.) (rpm) (s) (° C.) Example 1 2500 360 252500 360 25 Example 2 2500 360 25 2500 360 25 Example 3 2500 360 25 2500360 25 Example 4 2500 360 25 2500 360 25 Example 5 2500 300 25 2500 36025 Example 6 2500 300 25 2500 360 25 Example 7 2500 300 25 2500 360 25Example 8 2500 300 25 2500 360 25 Example 9 2500 300 25 2500 360 25Example 10 2500 300 25 2500 360 25 Example 11 2500 300 25 2500 360 25Example 12 2500 300 25 2500 360 25

TABLE 6 Addition of silica A Addition of silica B (first step) (secondstep) Rotation Stirring Rotation Stirring speed time Temperature speedtime Temperature (rpm) (s) (° C.) (rpm) (s) (° C.) Example 13 2500 30025 2500 360 25 Example 14 2500 300 25 2500 360 25 Example 15 2500 300 252500 360 25 Example 16 2500 300 25 2500 360 25 Example 17 2500 300 252500 360 25 Example 18 2500 300 25 2500 360 25 Example 19 2000 300 252500 360 25 Example 20 2500 300 25 2000 300 25 Example 21 2000 300 252500 300 25 Example 22 3000 300 25 2000 300 25 Example 23 3000 300 253000 300 25

TABLE 7 Addition of silica A Addition of silica B (first step) (secondstep) Rotation Stirring Rotation Stirring speed time Temperature speedtime Temperature (rpm) (s) (° C.) (rpm) (s) (° C.) Comparative 2500 30025 2500 360 25 Example 1 Comparative 2500 300 25 2500 360 25 Example 2Comparative 2500 300 25 2500 360 25 Example 3 Comparative 2500 300 252500 360 25 Example 4 Comparative 2500 300 25 2500 360 25 Example 5Comparative 2500 300 25 2500 360 25 Example 6 Comparative 2500 300 252500 360 25 Example 7 Comparative 2500 300 25 2500 360 25 Example 8Comparative 2500 300 25 2500 360 25 Example 9 Comparative 2500 300 252500 360 25 Example 10 Comparative 2500 300 25 2500 360 25 Example 11

TABLE 8 Addition of silica A Addition of silica B (first step) (secondstep) Rotation Stirring Rotation Stirring speed time Temperature speedtime Temperature (rpm) (s) (° C.) (rpm) (s) (° C.) Comparative 2500 30025 2500 360 25 Example 12 Comparative 2500 300 25 2500 360 25 Example 13Comparative 2500 300 25 2500 360 25 Example 14 Comparative 2500 300 252500 360 25 Example 15 Comparative 2500 300 25 2500 360 25 Example 16Comparative 2500 300 25 2500 360 25 Example 17 Comparative 2500 300 252500 360 25 Example 18 Comparative 2000 240 25 2500 360 25 Example 19Comparative 2500 300 25 2000 240 25 Example 20 Comparative 2000 180 252500 480 25 Example 21 Comparative 3000 480 25 2000 300 25 Example 22

A method of measuring the residual ratio X and the residual ratio Y willbe described.

The residual ratio X and the residual ratio Y were calculated accordingto the following equations.

Residual Ratio X=(N _(a2) /N _(a1))×100  Equation (1)

Residual Ratio Y=(N _(b2) /N _(b1))×100  Equation (2)

In the equation (1), N_(a1) is the number of adhered silica A measuredfor the toner according to each Example, and N_(a2) is the number ofadhered silica A measured for a particle z obtained by the followingmethod Z.

In the equation (2), N_(b1) is the number of adhered silica B measuredfor the toner according to each Example, and N_(b2) is the number ofadhered silica B measured for the particle z obtained by the followingmethod Z.

N_(a1), N_(a2), N_(b1), and N_(b2) represent the number of each adheredsilica in the scanning electron microscope (SEM) image. Specifically,the number was observed by an SEM (“ULTRA 55” manufactured by ZEISS) ata magnification of 50,000 times. A frame of 1 μm×1 μm (1 μm²) wasprovided on the field of view, and the number of silica particlespresent in this frame was measured for each of various types of silica.

Method Z: 11 g of the toner according to each Example, 56.8 g of ionexchange water, and 12.8 g of a surfactant were added to a 100 ml beakerand were mixed, and the mixture was stirred using a magnetic stirreruntil a toner layer on a liquid surface disappeared, thereby preparing adispersion liquid. This is a dispersing step for the toner. As thesurfactant, a “Yashinomi Detergent” manufactured by SALAYA was used.

Next, the dispersion liquid was subjected to an ultrasonic treatmentusing an ultrasonic cleaner (ASONE US-1R) at 20° C. and 1000 Hz for 10minutes. This is an impact step for the toner.

After the impact step, the dispersion liquid was poured into twocentrifugal tubes, and ion exchange water was added to each centrifugaltube such that the liquid was 45 ml. The centrifugal tube wascentrifuged at 20° C. and 1000 rpm for 15 minutes. As a centrifugalseparator, a “HSIANG TAI-CN-2060” manufactured by ASONE Corporation wasused. Thereafter, a supernatant in the centrifugal tube was removed bydecantation, and ion exchange water was added such that the liquid was45 ml, followed by stirring again. These operations were furtherexecuted twice. Thereafter, the detached external additive wasseparated, and filtration and washing were executed by adding 100 ml ofion exchange water. For the filtration, ADVANTEC GC90 paper was used.After the washing, vacuum drying was executed at 30° C. for 8 hours toobtain the particle z.

The crystalline polyester resin and the amorphous polyester resin usedin Examples are as follows.

-   -   Crystalline polyester resin (mass average molecular weight:        9.5×10³, melting point: 100° C.)    -   Amorphous polyester resin (mass average molecular weight:        20×10³, melting temperature: 110° C.)

A method of measuring the melting point of the crystalline polyesterresin will be described.

The crystalline polyester resin was measured by a DSC “DSC Q2000(manufactured by TA Instruments)”. Measurement conditions are asfollows.

Amount of sample: 5 mg.

Lid and pan: alumina.

Temperature raising rate: 10° C./min.

Measuring method: the temperature of the sample was raised from 20° C.to 200° C. Thereafter, the sample was cooled to 20° C. or lower. Thesample was heated again, and a maximum endothermic peak temperaturemeasured in a temperature range of about 75° C. to 120° C. was definedas the melting point of the crystalline polyester resin.

A method of measuring the melting temperature of the amorphous polyesterresin will be described.

The toner according to each Example was molded into a pellet shape byapplying a pressure with a pressure applying machine. For the pellet,the melting temperature of the amorphous polyester resin was measuredusing a flow tester “CFT-500D, manufactured by Shimadzu Corporation”under the following conditions.

Measurement start temperature: 30° C.

Measurement end temperature: 200° C.

Load: 10 kgf

Temperature raising rate: 10° C./min

In the flow tester, a temperature corresponding to a midpoint (½)between an outflow start temperature at which a melt outflow started andan outflow end temperature at which the entire sample was melted andflowed out was defined as the melting temperature.

A method of measuring a carbon atom distribution (a ratio of the estercompound having each number of carbon atoms) of the ester compoundconstituting the ester wax will be described.

0.5 g of the toner according to each Example was weighed andaccommodated in an Erlenmeyer flask. Next, 2 mL of methylene chloridewas added to the Erlenmeyer flask to dissolve the toner. Further, 4 mlof hexane was added to the Erlenmeyer flask to prepare a mixed liquid.The mixed liquid was filtered and separated into a filtrate and aninsoluble matter. The solvent was distilled off from the filtrate undera nitrogen stream to obtain a precipitate. For the precipitate, thecarbon atom distribution of the ester compound in the ester waxextracted from the toner was measured.

The ratio of the ester compound having each number of carbon atoms wasmeasured by FD-MS “JMS-T100GC” (manufactured by JEOL Ltd.). Measurementconditions are as follows.

Concentration of sample: 1 mg/ml (solvent: chloroform).

Cathode voltage: −10 kv.

Spectrum recording interval: 0.4 s.

Measurement mass range (m/z): 10 to 2000.

A total ion strength of the ester compound having each number of carbonatoms obtained by the measurement was defined as 100. A relative valueof the ion strength of the ester compound having each number of carbonatoms with respect to the total ion strength was determined. Therelative value was defined as the ratio of the ester compound havingeach number of carbon atoms in the ester wax. The number of carbon atomsin the ester compound having the maximum relative value was representedby C₁.

A method of analyzing the first monomer group and the second monomergroup will be described.

1 g of each ester wax was subjected to a methanolysis reaction at atemperature of 70° C. for 3 hours. A product after the methanolysisreaction was subjected to mass spectrometry by FD-MS to determine acontent of the long-chain alkylcarboxylic acid having each number ofcarbon atoms and a content of the long-chain alkyl alcohol having eachnumber of carbon atoms.

A method of measuring a carbon atom distribution (a ratio of thecarboxylic acid having each number of carbon atoms) of the carboxylicacid constituting the first monomer group will be described.

The ratio of the carboxylic acid having each number of carbon atoms wasmeasured by FD-MS “JMS-T100GC” (manufactured by JEOL Ltd.). Measurementconditions are as follows.

Concentration of sample: 1 mg/ml (solvent: chloroform).

Cathode voltage: −10 kv.

Spectrum recording interval: 0.4 s.

Measurement mass range (m/z): 10 to 2000.

A total ion strength of the carboxylic acid having each number of carbonatoms obtained by the measurement was defined as 100. A relative valueof the ion strength of the carboxylic acid having each number of carbonatoms with respect to the total ion strength was determined. Therelative value was defined as the ratio of the carboxylic acid havingeach number of carbon atoms in the ester wax. The number of carbon atomsin the carboxylic acid having the maximum relative value was representedby C_(n).

A method of measuring a carbon atom distribution (a ratio of the alcoholhaving each number of carbon atoms) of the alcohol constituting thesecond monomer group will be described.

The ratio of the alcohol having each number of carbon atoms was measuredby FD-MS “JMS-T100GC” (manufactured by JEOL Ltd.). Measurementconditions are as follows.

Concentration of sample: 1 mg/ml (solvent: chloroform).

Cathode voltage: −10 kv.

Spectrum recording interval: 0.4 s.

Measurement mass range (m/z): 10 to 2000.

A total ion strength of the alcohol having each number of carbon atomsobtained by the measurement was defined as 100. A relative value of theion strength of the alcohol having each number of carbon atoms withrespect to the total ion strength was determined. The relative value wasdefined as the ratio of the alcohol having each number of carbon atomsin the ester wax. The number of carbon atoms in the alcohol having themaximum relative value was represented by C_(n).

The ester waxes A1 to A12 and B1 to B8 used in Examples will bedescribed.

In all of the ester waxes A1 to A12, the number of carbon atoms C₁ ofthe ester compound having the maximum content was 44, the number ofcarbon atoms C_(n) of the carboxylic acid having the maximum content inthe first monomer group was 22, and the number of carbon atoms C_(m) ofthe alcohol having the maximum content in the second monomer group was20.

For the ester waxes A1 to A12, the carbon number distribution of theester wax had only one maximum peak in a region having 43 or more carbonatoms.

Properties of the ester waxes A1 to A12 obtained based on measurementresults of mass distribution are shown in Table 9. Properties of theester waxes B1 to B8 are shown in Table 10.

TABLE 9 a1 a2 b1 b2 c1 c2 Ester wax A1 4 4 3 15 82.5 80 Ester wax A2 4 40 15 82.5 80 Ester wax A3 4 4 5 15 82.5 80 Ester wax A4 4 4 3 0 82.5 80Ester wax A5 4 4 3 20 82.5 80 Ester wax A6 3 3 3 15 82.5 80 Ester wax A74 3 3 15 70 80 Ester wax A8 4 3 3 15 95 80 Ester wax A9 4 3 3 15 82.5 70Ester wax A10 4 3 3 15 82.5 90 Ester wax A11 4 3 3 15 82.5 80 Ester waxA12 4 4 3 15 82.5 80

TABLE 10 a1 a2 b1 b2 c1 c2 Ester wax B1 4 4 6 15 82.5 80 Ester wax B2 44 3 21 82.5 80 Ester wax B3 2 3 3 15 82.5 80 Ester wax B4 3 2 3 15 82.580 Ester wax B5 4 4 3 15 69 80 Ester wax B6 4 4 3 15 96 80 Ester wax B74 4 3 15 82.5 69 Ester wax B8 4 4 3 15 82.5 91

In Tables 9 and 10, a₁ is the number of types of carboxylic acids in thefirst monomer group. a₂ is the number of types of alcohols in the secondmonomer group. b₁ is a total ratio [% by mass] of the carboxylic acidhaving 18 or less carbon atoms with respect to 100% by mass of the firstmonomer group. b₂ is a total ratio [% by mass] of the alcohol having 18or less carbon atoms with respect to 100% by mass of the second monomergroup. c₁ is a ratio [% by mass] of the carboxylic acid having C_(n)carbon atoms with respect to 100% by mass of the first monomer group. c₂is a ratio [% by mass] of the alcohol having C_(m) carbon atoms withrespect to 100% by mass of the second monomer group.

A method of measuring the average primary particle diameters D₅₀ of thesilica A and the silica B will be described.

A laser diffraction particle size distribution measuring device(manufactured by Shimadzu Corporation (SALD7000)) was used.

The developer according to Examples will be described.

8.5 parts by mass of the toner according to each Example was stirredwith respect to 100 parts by mass of a ferrite carrier by a turbo mixerto obtain the developer according to each Example. A surface of theferrite carrier is coated with a silicone resin having an averageparticle diameter of 40 μm.

A method of evaluating the low-temperature fixability will be described.

The developer according to each Example was accommodated in a tonercartridge. The toner cartridge was disposed in an image formingapparatus for evaluating the low-temperature fixability. The imageforming apparatus for evaluating the low-temperature fixability isobtained by modifying a commercially available e-studio 5018A(manufactured by TOSHIBA TEC CORPORATION) such that a fixing temperaturecan be changed from 100° C. to 200° C. in an increment of 0.1° C. Theimage forming apparatus for evaluating the low-temperature fixabilitywas used, the fixing temperature was set to 150° C., and ten solidimages having a toner adhered amount of 1.5 mg/cm² were obtained. Whenno image peeling due to offset and unfixed state occurred in all of theten solid images, the set temperature was lowered by 1° C., and a solidimage was obtained in the same manner as described above. The operationwas repeated to determine a lower limit temperature of the fixingtemperature at which no image peeling occurred in the solid image, andthe lower limit temperature was defined as a minimum fixing temperatureof the toner. When the minimum fixing temperature was 120° C. or lower,the low-temperature fixability of the toner was evaluated as acceptable(good). When the minimum fixing temperature was higher than 120° C., thelow-temperature fixability of the toner was evaluated as unacceptable(poor).

A method of evaluating the storage stability in a high-temperatureenvironment will be described.

When evaluation results of the following four items of “heatresistance”, “conveyance property”, “toner scattering”, and “imagedensity” were all acceptable (good), the storage stability in ahigh-temperature environment was evaluated to be excellent.

A method of evaluating the “heat resistance” will be described.

The toner according to each Example was allowed to stand at 55° C. for10 hours. After allowing the toner to stand at 55° C. for 10 hours, 15 gof the toner was sieved with a mesh having an opening of 0.07 mm, andthe toner remaining on the mesh was weighed. The smaller the amount ofthe toner remaining on the mesh, the less the aggregation and the betterthe heat resistance. When the amount of the toner remaining on the meshwas 3 g or less, the heat resistance of the toner was evaluated asacceptable (good). When the amount of the toner remaining on the meshwas more than 3 g, the heat resistance of the toner was evaluated asunacceptable (poor).

A method of evaluating the “conveyance property” will be described.

A commercially available e-studio 5018A (manufactured by TOSHIBA TECCORPORATION) was used, and a temperature of a developing unit Dc-Sl wasadjusted to be saturated at 47° C. Then, while the recycling system wasoperated, 30,000 sheets of A4-size images with a printing ratio of 8%were printed on both sides under a high-temperature and high-humidityenvironment, and the temperature of the developing unit Dc-Sl wasadjusted to be maintained at 47° C. by adjusting an air volume of acooling fan. An image density difference after printing the 30,000sheets of images was measured with a densitometer (“eXact” manufacturedby X-Rite Co., Ltd.). The image density of the solid image was measuredby a densitometer every 1 cm in a main scanning direction, and adifference between a maximum value and a minimum value of all thesevalues was obtained.

When the image density difference was less than 0.8, the conveyanceproperty of the developer was evaluated as acceptable (good). When theimage density difference was 0.8 or more, the conveyance property of thedeveloper was evaluated as unacceptable (poor).

A method of evaluating the “toner scattering” will be described.

A commercially available e-studio 5018A (manufactured by TOSHIBA TECCORPORATION) was used, and a document having a printing ratio of 8.0%was continuously copied on 200,000 sheets of A4 paper. Thereafter, thetoner deposited on a lower side of a magnet roller of the developingunit was sucked by a vacuum cleaner, and an amount of the depositedtoner was measured as an amount of scattered toner. When the amount ofscattered toner was 170 mg or less, the charge amount of the toner wasevaluated as acceptable (good). When the amount of scattered toner wasmore than 170 mg, the charge amount of the toner was evaluated asunacceptable (poor).

A method of evaluating the “image density” will be described.

The developer according to each Example was allowed to stand in athermostatic chamber at a temperature of 10° C. and a humidity of 20%for 24 hours, and then accommodated in a toner cartridge. The tonercartridge was disposed in a commercially available e-studio 5018A(manufactured by TOSHIBA TEC CORPORATION). After 100 sheets of chartshaving a printing ratio of 10% were printed, a solid image of A4 sizewas printed, and image densities at four corners and the center of theimage were measured with a densitometer (“eXact” manufactured by X-RiteCo., Ltd.), and an average value of these five positions was obtained.When the average value of the image densities was 1.0 or more, the imagedensity was evaluated as acceptable (good). When the average value ofthe image densities was less than 1.0, the image density was evaluatedas unacceptable (poor).

Evaluation results of the low-temperature fixability, the heatresistance, the conveyance property, the toner scattering, and the imagedensity of the toner according to each Example are shown in Tables 1, 2,3, and 4.

The toners according to Examples 1 to 23 have excellent low-temperaturefixability and excellent storage stability in a high-temperatureenvironment. The e-studio 5018A is an image forming apparatus thatrecycles the toner. Therefore, the toners according to Examples 1 to 23are excellent in storage stability in a high-temperature environmenteven when recycled, and is capable of sufficiently maintaining thecharge amount.

In contrast, the toners according to Comparative Examples 1 to 22 didnot reach acceptance criteria at the same time in all of thelow-temperature fixability, the heat resistance, the conveyanceproperty, the toner scattering, and the image density.

With respect to any figure or numerical range for a givencharacteristic, a figure or a parameter from one range may be combinedwith another figure or a parameter from a different range for the samecharacteristic to generate a numerical range.

Other than in the operating examples, if any, or where otherwiseindicated, all numbers, values and/or expressions referring toparameters, measurements, conditions, etc., used in the specificationand claims are to be understood as modified in all instances by the term“about.”

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of thedisclosure. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the disclosure.

What is claimed is:
 1. A toner, comprising: a toner mother particle; andan external additive adhered to a surface of the toner mother particle,wherein the toner mother particle comprises a crystalline polyesterresin, an ester wax, and a colorant, the external additive comprisessilica A having an average primary particle diameter D₅₀ of 10 nm to 14nm and monodispersed silica B having an average primary particlediameter D₅₀ of 90 nm to 150 nm, the ester wax comprises a condensationpolymer of a first monomer group including at least three types ofcarboxylic acids and a second monomer group including at least threetypes of alcohols, a ratio of a carboxylic acid having 18 or less carbonatoms in the first monomer group is 5% by mass or less with respect to100% by mass of the first monomer group, a ratio of an alcohol having 18or less carbon atoms in the second monomer group is 20% by mass or lesswith respect to 100% by mass of the second monomer group, a ratio of acarboxylic acid having C_(n) carbon atoms, which is a maximum content inthe first monomer group, is 70% by mass to 95% by mass with respect to100% by mass of the first monomer group, a ratio of an alcohol havingC_(m) carbon atoms, which is a maximum content in the second monomergroup, is 70% by mass to 90% by mass with respect to 100% by mass of thesecond monomer group, a content of the silica A is 0.1 parts by mass to0.8 parts by mass with respect to 100 parts by mass of the toner motherparticle, a content of the silica B is 0.3 parts by mass to 1.2 parts bymass with respect to 100 parts by mass of the toner mother particle, aratio of the content of the silica B to the content of the silica A is1.0 to 5.0, a residual ratio X of the silica A calculated according tothe following equation (1) is 70% or more, a residual ratio Y of thesilica B calculated according to the following equation (2) is 30% ormore, and a ratio of the residual ratio X to the residual ratio Y is 1.0to 3.0,Residual Ratio X=(N _(a2) /N _(a1))×100  Equation (1)Residual Ratio Y=(N _(b2) /N _(b1))×100  Equation (2) in the equation(1), N_(a1) is a number of adhered silica A measured for the toner, andN_(a2) is a number of adhered silica A measured for a particle zobtained by a following method Z, and in the equation (2), N_(b1) is anumber of adhered silica B measured for the toner, and N_(b2) is anumber of adhered silica B measured for the particle z obtained by thefollowing method Z, Method Z: executing an ultrasonic treatment on anaqueous liquid containing the toner, water, and a surfactant at 20° C.and 1000 Hz for 10 minutes, then centrifuging the obtained aqueousliquid at 20° C. and 1000 rpm for 15 minutes, removing the separatedexternal additive, and then executing drying to obtain the number ofadhered silica for particle z.
 2. The toner according to claim 1,wherein the toner mother particle further comprises an amorphouspolyester resin.
 3. The toner according to claim 1, wherein a total ofthe content of the silica A and the content of the silica B is 0.5 partsby mass to 1.7 parts by mass with respect to 100 parts by mass of thetoner mother particle.
 4. A toner cartridge comprising the toneraccording to claim
 1. 5. An image forming apparatus comprising the toneraccording to claim
 1. 6. The toner according to claim 1, wherein thealcohol comprises one or more of: ethylene glycol, 1,2-propylene glycol,1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,neopentyl glycol, 1,4-butenediol, polyoxypropylene, polyoxyethylene,glycerin, pentaerythritol, and trimethylolpropane.
 7. The toneraccording to claim 1, wherein the carboxylic acid comprises one or moreof: adipic acid, oxalic acid, malonic acid, maleic acid, fumaric acid,citraconic acid, itaconic acid, glutaconic acid, succinic acid, phthalicacid, isophthalic acid, terephthalic acid, sebacic acid, azelaic acid,succinic acid substituted with an alkyl group or an alkenyl group,cyclohexanedicarboxylic acid, trimellitic acid, and pyromellitic acid;acid anhydrides thereof; and esters thereof.
 8. The toner according toclaim 1, wherein the melting point of the crystalline polyester resin isfrom 60° C. to 120° C.
 9. A method of making toner comprising a tonermother particle and an external additive adhered to a surface of thetoner mother particle, comprising: combining a toner mother particle andan external additive so that external additive adheres to a surface ofthe toner mother particle, wherein the toner mother particle comprises acrystalline polyester resin, an ester wax, and a colorant, the externaladditive comprises silica A having an average primary particle diameterD₅₀ of 10 nm to 14 nm and monodispersed silica B having an averageprimary particle diameter D₅₀ of 90 nm to 150 nm, the ester waxcomprises a condensation polymer of a first monomer group including atleast three types of carboxylic acids and a second monomer groupincluding at least three types of alcohols, a ratio of a carboxylic acidhaving 18 or less carbon atoms in the first monomer group is 5% by massor less with respect to 100% by mass of the first monomer group, a ratioof an alcohol having 18 or less carbon atoms in the second monomer groupis 20% by mass or less with respect to 100% by mass of the secondmonomer group, a ratio of a carboxylic acid having C_(n) carbon atoms,which is a maximum content in the first monomer group, is 70% by mass to95% by mass with respect to 100% by mass of the first monomer group, aratio of an alcohol having C_(n) carbon atoms, which is a maximumcontent in the second monomer group, is 70% by mass to 90% by mass withrespect to 100% by mass of the second monomer group, a content of thesilica A is 0.1 parts by mass to 0.8 parts by mass with respect to 100parts by mass of the toner mother particle, a content of the silica B is0.3 parts by mass to 1.2 parts by mass with respect to 100 parts by massof the toner mother particle, a ratio of the content of the silica B tothe content of the silica A is 1.0 to 5.0, a residual ratio X of thesilica A calculated according to the following equation (1) is 70% ormore, a residual ratio Y of the silica B calculated according to thefollowing equation (2) is 30% or more, and a ratio of the residual ratioX to the residual ratio Y is 1.0 to 3.0,Residual Ratio X=(N _(a2) /N _(a1))×100  Equation (1)Residual Ratio Y=(N _(b2) /N _(b1))×100  Equation (2) in the equation(1), N_(a1) is a number of adhered silica A measured for the toner, andN_(a2) is a number of adhered silica A measured for a particle zobtained by a following method Z, and in the equation (2), N_(b1) is anumber of adhered silica B measured for the toner, and N_(b2) is anumber of adhered silica B measured for the particle z obtained by thefollowing method Z, Method Z: executing an ultrasonic treatment on anaqueous liquid containing the toner, water, and a surfactant at 20° C.and 1000 Hz for 10 minutes, then centrifuging the obtained aqueousliquid at 20° C. and 1000 rpm for 15 minutes, removing the separatedexternal additive, and then executing drying to obtain the number ofadhered silica for particle z.
 10. The method according to claim 9,wherein the toner mother particle further comprises an amorphouspolyester resin.
 11. The method according to claim 9, wherein a total ofthe content of the silica A and the content of the silica B is 0.5 partsby mass to 1.7 parts by mass with respect to 100 parts by mass of thetoner mother particle.
 12. A toner cartridge comprising the toner madeaccording to claim
 9. 13. An image forming apparatus comprising thetoner made according to claim
 9. 14. The method according to claim 9,wherein the alcohol comprises one or more of: ethylene glycol,1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-butenediol,polyoxypropylene, polyoxyethylene, glycerin, pentaerythritol, andtrimethylolpropane.
 15. The method according to claim 9, wherein thecarboxylic acid comprises one or more of: adipic acid, oxalic acid,malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid,glutaconic acid, succinic acid, phthalic acid, isophthalic acid,terephthalic acid, sebacic acid, azelaic acid, succinic acid substitutedwith an alkyl group or an alkenyl group, cyclohexanedicarboxylic acid,trimellitic acid, and pyromellitic acid; acid anhydrides thereof; andesters thereof.
 16. The method according to claim 9, wherein the meltingpoint of the crystalline polyester resin is from 60° C. to 120° C.